<!DOCTYPE html>
<html>
<head>
    <title>Iframe page without source</title>
</head>
<body>
<iframe id="iframe" height="500px" width="800px"></iframe>
</body>
<script>
    document.addEventListener('DOMContentLoaded', function () {
        var iframe = document.getElementById('iframe');
        var body   = iframe.contentWindow.document.body;

        body.innerHTML = '\<input id="input">';
    });
</script>
</html>